I think the Brady Retirement Party shut the door on another return. One more season would have been nice but it's not happening. Miami seems committed to Tua even though he has admittedly considered retirement (which probably will come to fruition within the next couple of seasons). The Raiders are (foolishly) on to Garoppolo (and Brady has expressed disinterest in becoming a Raider anyway). And it doesn't seem like the power that be in SF (i.e. Shanahan) are really interested in Brady. The bridge to Foxboro was burnt down after 2019. There's nowhere else to be considered.
I've always said that Brady was going to have a pretty hard time dealing with becoming irrelevant. His being coy and dangling the carrot, is his way of trying to stay in the spotlight.